Fix IDE edge functions

[fabianbs96]

AllBottom::composeWith did not correctly model function composition semantics in most of phasar's IDE analyses. This PR fixes this. For future IDE implementations keep the following insights in mind:

• On $Λ \rightarrow Λ$ edges always attach the EdgeIdentity
• For any edge functions $f$ and $g$ and edge value $l$ it should hold: $f$-> $composeWith(g)$-> $computeTarget(l) == g$-> $computeTarget(f$-> $computeTarget(l))$, especially:
• Any edge function $f$ composed with AllBottom should result in AllBottom
• Any edge function $f$ composed with EdgeIdentity should result in $f$
• AllBottom should only be composed with AllBottom or EdgeIdentity, otherwise there is a bug in the analysis
• Policies such as F::composeWith(G) calling G::composeWith(F) are bad and lead to hard-to-find bugs

[pdschubert]

Is this still a draft or can I start reviewing it?